Process for the manufacture of porous, air-permeable, flexible sheet material



Oct. 4, 1955 c. L. NOTTEBOHM 2,719,806

PROCESS FOR THE MANUFACTURE OF POROUS, AIR-PERMEABLE, FLEXIBLE SHEET MATERIAL Filed Dec. 22, 1951 INVENTOR. Curl Ludwig Nottebohm BY ATTORNEYS United States Patent PROCESS FOR THE MANUFACTURE OF POROUS, AlR-PERMEABLE, FLEXIBLE SHEET MATERIAL Carl Ludwig Nottebohm, Weinheim .an der Bergstrasse, Germany, assignor to Pellon Corporation, New York, N. Y., a corporation of New York Application December 22, 1951, Serial No. 262,941 Claims priority, application Germany October 1, 1948 Claims. (Cl. 154-101) My invention relates to a new process for the manufacture of porous, air-permeable, flexible sheet material.

The present application is a continuation-in-part of my co-pending United States patent applications Serial Nos. 102,423 and 102,425, both filed on June 30, .1949, both now abandoned.

One object of the invention is to produce a porous, air-permeable, flexible sheet material consisting of an open skeleton of fine, cardable, intermingled, polyposed fibers having substantially uniformly distributed there through small, filmy binder particles adhering to the fibers and cementing the fibers together at their crossing points without either completely encasing the fibers or filling the interstices therebetween. to any substantial extent.

Another object of the invention is to produce a thin, porous sheet material having a thickness of about 0.1 to about 3.5 mm.

Still another object of the invention is to produce a thin, porous sheet material having a light weight of from about 40 g. to about 1700 g. per square m.

A still further object of the invention is to produce a light, fibrous sheet material which is stabilized by relatively small, uniformly distributed binder particles located principally at the crossing points of the individual fibers and which contains relatively large proportions, such as from about 25% to about 75% by weight of fiber material.

Still a further object of the invention is to produce. a fibrous sheet material starting from very loose, light and thin fleeces which are made of fine, cardable, polyposed fibers and which have very little inherent stability, and stabilizing such fleeces by incorporation therein of about 33 /3 to 300 parts by weight of binder material per 100 parts by weight of fibers, said binder material being uniformly distributed throughout the fibrous skeleton in the form of small, filmy coating particles adhering to' the fibers, particularly at the crossing points between, adjacent fibers.

A particular object of the invention is to produce a sheet material which has a high absorptivity for water which may, if desired, be further increased with simultaneous strengthening of the sheet material by an aftertreatment with binder material as described in my United States patent application Serial No. 262,942, filed December 22, 1951, which is a continuation-in-part of my copending United States patent application Serial No. 102,424, filed June 30, 1949, now abandoned.

It has been found that a satisfactory, uniform impregnation of light, thin, loose fleeces consisting of intermingled, polyposed, fine cardable fibers with retention of numerous relatively large interstices between the fibers is frequently extremely difficult to accomplish. The thin fleeces are apt to be damaged if binder material is incorporated therein in liquid form by spraying with, or by immersion in, a liquid. If the liquid is viscous, it does not penetrate the fleece uniformly,and if a thinly flowing liquid is used, the impregnation tends to accumulate in the lower part of the fleece due to its gravity. Frequently, the light fleeces collapse or distintegrate com pletely under treatment with liquids and become deformed so that the interstices between the fibers are irregularly reduced and enlarged in size and maybe more or less filled with binder material, thus producing a thoroughly unsatisfactory product.

It is a special object of the present invention to obviate these disadvantages and to devise a process for the preparation of light, highly porous, fibrous sheet material which is simple and efficient, and which produces the desired results with a variety of fibers or fiber mixtures and also with a variety of binder materials.

According to my invention, a porous, air-permeable, flexible sheet material is produced by a process which comprises the following essential steps:

A loose fleece is prepared of intermingled, polyposed, fine, cardable fibers, said fleece weighingabout 35 g. :to about 1000 g. per square m. The loose fleece, which has very little stability of its own, is next pre-treated to produce a light surface cohesion without appreciable reduction in the porosity of the sheet. This may be accomplished, for instance, by making the fleece at least at one surface thereof of fibers which can be given adhesive properties by suitable treatment. Thus, thermoplastic fibers may be employed which are cohered by means 'of heat treatment or by spraying with acetone, or alginate fibers may be used which can be rendered cohesive by a treatment with soap solutions and drying. I prefer to obtain the desired light surface cohesion of the fleece by application to one surface thereof of a first binding agent in a carrier liquid and drying of the fleece to effect stabilization of the binder by removal of the carrier liquid. According to a preferred embodiment of my invention, the surface impregnation is effected by treating the surface of the fleece to be stabilized with a binder liquid in the form of a light, stable foam, which may contain from about 9 to 13 volume parts of gas per volume part of liquid.

This pre-treatment of one surface gives to the fleece sufiicient stability to make it resistant to the physical stresses of the next following through impregnating step. According to my invention, through impregnation is accomplished by pressing into the untreated surface of the fleece an aqueous binder material in the form of a stable, flowable foam under a pressure to effect a substantially complete and uniform penetration of the fleece with simultaneous destruction of part of the foam cells and preservation of numerous, relatively large interstices between the fibers.

While, in some instances, a substantially uniform impregnation of a loose fiber fleece may be accomplished by pressing foam .into a fleece superficially pretreated on one surface through the pretreated surface, or into a fleece superficially pretreated on both surfaces through one or both of the pretreated surfaces, it has been found that a satisfactory penetration of an aqueous binder foam into a fleece through a surface pretreated with even minute quantities of binder material can frequently not be accomplished without difliculties. The resistance ofiered by the pretreated surfaces to the penetration by the foam makes it necessary to use foams containing relatively small proportions of gas and which are made from liquid binder materials containing relatively small proportions of binder solids. comparatively high pressure is necessary to effect a complete penetration even of fight, flowable foam particles through a pretreated surface or pretreated surfaces and, as a result, the fiber. skeleton may" be compressed or condensed to an undesirable extent or even torn without being sufiiciently stabilized by binder particles precipitated at the crossing points of adjacent fibers.

It is therefore an essential feature of the present invention that the starting fleeces are superficially prestabilized on one surface only and the binder foam used for through-impregnation of the fleece is pressed into the fleece through the untreated surface thereof. This procedure permits the use of foams having a relatively high gas content and containing a higher proportion of solid binder material to liquid carrier. It also makes possible the use of relatively low pressures for a complete penetration of the fleece without undesirable condensation of the fleece or elimination of most of the interstices between the fibers and without destruction of the thin, loose fiber fleece.

After through impregnation, the sheet material is dried without pressure to remove the water from the finely distributed liquid particles formed by the partial destruction of the foam cells and from the remaining foam cells which are thus caused to collapse during the drying operation. As the foam is broken up, small filmy particles of binder material are deposited on the fibers and collect mainly at the crossing points between adjacent fibers where they find relatively large solid supports. Thus, a stabilized sheet structure is obtained in which a fiber skeleton has uniformly distributed therethrough relatively small, filmy binder particles positioned mainly at the crossing points between adjacent fibers and cementing the adjacent fibers securely together with retention of numerous, relatively large interstices between the fibers.

- A variety of fibers and fiber mixtures may be used for the preparation of the loose fiber fleeces. Suitable fibers are, for instance, vegetable fibers, such as cotton, flax, ra-

-mie and jute fibers; animal fibers, such as wool, goats hair,

camels hair or human hair; synthetic fibers, such as rayon, spun rayon, alginate fibers, superpolyamide fibers, polyvinyl fibers, polyvinylidene fibers, acrylonitrile fibers, protein fibers; or mineral fibers, such as glass, rock or asbestos fibers and the like. Mixture of two or more kinds of fibers in various proportions may be employed. Waste fibers, such as wool-comber waste, torn wool, cotton waste, torn cotton, etc., may also be used alone or in mixture with other fibers. It is an essential feature of my invention that the fibers used for the formation of the loose fleeces are fibers capable of being carded on ordinary carding machines. They should have a length of about 3 to 10 cm., and preferably about 4 to 6 cm., although mixtures containing some shorter fibers of about 1.5 to 3 cm. length have been found to give satisfactory results. Fibers, such as horsehair, cows hair, coconut fibers, etc., which are too long or which have hard and smooth surfaces rendering them unsuitable for carding on ordinary carding machines, should not be present in the fiber fleeces forming the starting material according to the present invention because such fibers cannot be satisfactorily formed into webs or fleeces.

The fleeces may be prepared on conventional carding machines and by conventional procedures.

For many purposes, it is preferred to prepare the fleece by laying upon one another several, e. g., from 2 to about 30 or more, thin webs of intermingled, polyposed fibers, each web having a thickness of about 0.1 to about 1.2 mm. and weighing about 5 g. to g. per square in. Preferably, adjacent webs are arranged at an angle to each other. The superposed webs are subjected to pressure and elevated temperature to cause them to cohere and to effect an initial condensation of the multi-layer structure formed. A slight longitudinal stretching by about 5 to 10% and a corresponding reduction in weight takes place during the formation of the multi-layer fleece.

The binder materials which have been found useful for the purpose of the present invention are film-forming substances which are capable of being dispersed or emulsified in aqueous carriers. Suitable binder materials are, for instance, natural rubber, new or reclaimed, the socalled synthetic rubbers, such as polybutadienestyrene,

polybutadieneacrylonitrile, chloroprene, the so-called thermoplastic synthetic resins, such as the polyvinyl esters, the polyvinylidene esters, the polyacrylates, polystyrene and the like, or mixtures of such materials. The binders are preferably used in the form of their aqueous emulsions or dispersions.

For the purposes of through impregnation, the aqueous binding agents, which may contain about 14% to about 40% by weight of solid binder material, and to which up to about 60 parts by weight of a wetting agent per 100 parts by weight of binder solids may be added, are first converted into a stable, flowable foam containing, for instance, about 2-12 volumes of gas per volume of binder liquid. If the binder material is vulcanizable, a vulcanizing agent and, if desired, a vulcanization accelerator, may be incorporated into the binder liquid before conversion thereof into a foam, and the binder in the fully impregnated sheet may be subjected to vulcanization without pressure during or after the drying of the foam impregnation.

The process according to the invention is illustratively exemplified in the accompanying drawings, in which:

Fig. 1 illustrates diagrammatically the various steps of the invention, as carried out in a continuous process; and

Fig. 2 shows, also diagrammatically, a detail of the apparatus illustrated in Fig. 1 on a larger scale.

Referring to the drawings, and first to Fig. 1, 11, 12, 13 and 14 are loose webs of fine, carded, fibers which are arranged in a plurality of intersecting directions, i. e., polyposed, the four webs being shown superposed upon one another to form a laminated structure. The laminated structure 15 is passed between two heated rollers 16, 17 which condense the multi-layer element with slight longitudinal stretching into a continuous fleece 18.

A light foam 19, containing about 9 to 13 volume parts of gas per volume part of liquid, is produced in a foam trough 20, and successive quantities of foam are pushed by blades 21, mounted on an endless conveyor 22, over the edge of the foam trough 20 and drop upon the upper surface of the fleece 18. As the fleece moves on, the foam is uniformly spread on the upper surface of the fleece, without any substantial penetration into the fleece, by means i of a stationary doctor blade 23. The fleece, now carrying on its surface a very fine layer of foam, is then passed into and through the drying chamber 24 where the collapsing foam solidifies to produce a light surface cohesion of the fleece without any appreciable reduction of its porosity. The quantity of binder material adhering to the surface of the fleece may amount to about 4 to about 17 g. per square m.

After leaving the drying chamber 24, the fleece is passed over a guide roller 25 and then between two pressure rollers 26, 27. As seen in both figures, the fleece runs first over the pressure roller 26 with its pre-treated surface in contact with the surface of the roller, and then into the nip formed between the two rollers 26, 27. A liquid binder, such as a latex emulsion, containing about 14 to 40 parts by weight of solid binder, 100 parts by weight of latex and suitable'quantities of wetting agents, vulcanizing agents, vulcanization accelerators, foam stabilizers and anti-oxidants, is converted into a flowable foam, having approximately the consistency of a heavy cream and containing about 2 to 12 volume parts of gas per volume part of liquid, in a foam chamber 28. The foam is passed through a conduit 29 into a foam-collecting trough'3l) from which it flows into the nip between the rollers 26, 27 upon the untreated surface of the fleece 18. As the fleece advances through the restricted passage between the rollers 26, 27 the foam is pressed into the fleece with a pressure causing substantially complete and uniform penetrationof the fleece by the foam and partial destruction of the foam cells. Dependent upon the adjustment of the pressure rollers and the width of the constricted passage formed between thennthe quantity of solid binder incorporated into the fleece during this foam impregnation may vary from about 26 to-about 287 parts (solid weight) per 100 parts by weight of fibers. :Simultarreouslyythe thickness of the fleece is reduced, but numerous relatively large interstices are preserved between the fibers.

Afterthe fleece has passed between the pressure rollers 26,27, it is returned to the drying chamber 24 for drying without pressure. In the chamber 24, the web is passed over a reversing roller 31' and out of thechamber over guide rollers 32, 33.

In the course of its treatment, including the preliminary surface treatment through impregnation anddrying', the material is stretched longitudinally beyondv its original length byabout 17.5 to about-1-00-% with acorresponding reduction in fiber weight per square m. of about 15% to about 50%.

The finished product is finally wound upona reel 34, and, if desired, vulcanized without pressure.

The following specific examples may serve to illustrate the invention butare not intended to limit its scope:

Example 1 Liquid .Solid Parts Parts .13. W. B. W

Polybutadienestyrene latex (40%) 250 .100 softened water .691. 5 Sodium isobutylene-naphthalene-sulfonate (wetting agent)... 50 -50 zinc oxide 5 5 colloidal sulphur 2. 5 2. 5 ultravulcanization accelerator: l g l The mixture contains about parts by weight of binder solids in 100 parts by weight of liquid.

The fleece is dried to produce a slight surface cohesion on the treated surface without any appreciable reduction of its porosity. About parts by weight of binder solids adhere to the surface of the fleece per 100 parts .by weight of fibers (10 g. per square m.).

The fleece is then treated by pressing into its untreated surface a relatively thick, but still easily flowable, foam containing about 6 volumes of air per volume of a liquid, film-forming binder containing about 35% by weight of binder solids and about 8% by weight of a wetting agent and having the following composition:

Thefoam is pressed into the fleece with a pressure to cause substantially complete and uniform penetration of the fleece with destruction of part of the foam cells.

Approximately 52 parts by weight of binder material (solid weight) are incorporated into the .fleecefor each 100 parts by weightof fibers.

The impregnated fleece is then dried by means of heat without pressure to cause a collapse bf ihl remaining foam cells and-a deposition of filmy,-solid.:hmder particles on the fibers, particularlyiat the'cross'ing points between adjacent fibers. l

During the several impregnating and drying'istz'tges-itlie material is stretched about 43% beyond its originallerigth, so that its fiber content-per. square m. at-the end is 'abou-t 30% less than that :of the starting fleece. The resulting sheet material is vulcanized without pressure, .then'was'he'd with water at a temperature ,of about 50 C., and dried. The dry sheet material is calendered under moderate pressure, rolled'o'n reels and completely-vulcanized 'by' 12 hourstorage-in aroom'he'a-ted to" C.

The finished product, which has a thickness of 0.15 mm, consists of a fiber skeleton having'small, lilmy binder particles distributed uniformly there'thro'ugh and adhering to the' fibers mainly at the crossing points-between adjacent fibers, thus cementing: the adjacent fibers together. The sheet material contains about 40% by weight of solid binder material and 60% by weight of fiber material. It weighs' about'80 g. per squ a r'em." material may be used for-reinforcing foil material, such as paper foils.

Example 2 A fiber mixture, consisting of 70 parts by weight of torn jute and 30.parts by weight of spun rayon, is formed into webs havingeaeh a thickness-M03 mar-ands weight of19g1persquar'e m. 4

Eight such webs are combined with pressure, .heat and slight longitudinal stretching into a fflee'ce having a weight of 140 g. per square m.

The fleeceis treated on one surface with a foam comprising about l2'volume parts of. airand one volume part of a liquid, film-forming binder material containing 1.0% by weight of binder solids and having the following composition: I

1 Liquid ,"SolidvParts 1 Parts BCW. B. W.

polymethylmethacrylate(40%) 250 "I00 softened water. 743 fatty alcohol suit 6 6 methylcell 1 1 After drying andsolidifioat'ionof the surface impregnation, which causes a surface deposition of'about '6 parts by Weight of solid binder material per l00pa rtsby weight of fibers (8.4 g. per square in), a fiowable foam con taining about 7 volume parts of air per volume part of liquid binder is pressed into the untreated surface of the fleece. The liquid binder which contains about 20% by weight of binder solids and about 2.4% of weight of a wetting agent has the following composition:

Liquid Solid Parts fParts natural rubber latex (60%) 164 softened water 308 .s..

paraffin emulsion (60%) I 5 3 polyethyleneoxy derivative (emulsifying agent)- 2 2 sodium isobutylene-naphthalene-sulfonate (wetting agent) 10 10 zinc oxide 5 [5 colloidal sulphur i 3- "3 ultravulcanization accelerator 1 -1 phenyi-beta-naphthyl-amine (anti-oxidant) '2 2 The impregnated sheet is stabilized by heating andpdrying without pressure suflicient to effect a partial vulcanh zationof the rubbenlightly calendered, and then washed in a textile washingmachine with water at 50 C. There after, it is dried on drying cylinders and then wound into rolls of about 200m. each,-wliich are stored for 12 hours in a room heated to about 80 C., to complete the vulcanization of the rubber. The sheet is finally smoothed on both sides by passing it between two rotating calender rollers. The finished sheet has a thickness of about 0.4 mm.

Example 3 A fiber mixture containing about 50 parts by weight of cotton waste and about 50 parts by weight of denatured flax fibers is formed .into webs having a thickness of about 0.8 mm. and weighing about 27 g. per square m. 12 such webs are laid on top of each other at an angle and passed with light longitudinal stretchingbetween heated rollers to form a multi-layer fleece which weighs about 300 g. per square m.

Thefleece is first treated on one surface with a foam containing 9 volume parts of air for each volume part of a 10% latex composition comprising:

Liquid Solid Parts Parts B. W. B. W.

natural rubber latex (73%) 137 100 softened water 835 alkyibenzene sulfonate (wetting agent).-- 18 18 zinc oxide 5 colloidal sulphur 3 3 ultravulcanization accelerator l 1 methyl cellulose 1 1 After drying, the pre-treated fleece has 3 parts by weight of solid rubber adhering to its surface per 100 parts by weight of fibers (9 g. per square m.).

This surface stabilized fleece is further impregnated by pressing into its untreated surface a flowable foam containing 3 volume parts of air per volume part of a 30% latex of the following composition:

About 63 parts (solid weight) of rubber are incorporated into the fleece per 100 parts by weight of fibers.

In the course of the treatment, the fleece is stretched longitudinally to about 125% of its original length with reduction of its thickness and a decrease of the fiber weight per square m. by about 20%. The product is then dried and vulcanized without pressure. The resulting, porous sheet material has a thickness of about 1.4 mm. and weighs about 421 g. per square m. It contains about 57% by weight of fibers, about 38% by Weight of solid natural rubber and about 5% by weight of wetting agent solids. The material is highly water absorbent and may be used in the manufacture of floor cloth.

Example 4 Cotton fibers are mixed with the same quantity of spun rayon fibers and worked into thin, loose webs of about 0.1 mm. thicknessweighing about 5 g. per square in. Twenty-four such webs are combined cross-wise with pressure and stretching into a fleece weighing about 108 g. per square in.

The fleece is treated first on one side with a relatively light foam containing 11 volume parts of air for each volume part of a 14% binder dispersion having the following composition:

Liquid Solid "Parts Parts B. W. B.

butadieneacrylonitrile polymer (37%) 265 100 softened water 428. 5 wetting agent. 20 20 zinc oxide 2. 6 2. 5 colloidal sulphur 2. 5 2. 5 ultravuloanization accelerator 1 1 antioxidants:

mercaptobenzimide 0. 2 0. 2 paraphenylenediamine derivative 0. 3 0.3

Upon drying, about 8 parts by weight of binder solids are deposited on the surface of the fleece per 100 parts by weight of fibers (8.6 g. per square m.).

Next, a heavier foam containing about 5 volumes of air per volume of liquid is pressed into the untreated surface of the fleece. This foam is made from a 25% dispersion having the same composition as the dispersion used for the pretreatment except that it contains, instead of 4285 parts by weight of softened water, only about 103.5 parts by weight of softened Water, and instead of 20 parts by weight of wetting agent, 25 parts by weight of wetting agent. About 74 parts by weight of solid binder material are incorporated into the fleece per 100 parts by weight of fibers.

The resulting porous sheet material is dried and vulcanized without pressure washed and dried again.

In the course of the treatment, the material is stretched longitudinally about 26% beyond the length of the originalfleece with a corresponding decrease in Weight of fibers per square on. by about 21%. The finished sheet material has a thickness of about 0.25 mm., weighs about 156 g. and contains about 45% by weight of binder solids.

The product is suitable for the washing of glass, china, etc.

Example 5 A fiber mixture consisting of 75% by weight of sheeps wool and 25% by weight of human hair'is formed into webs having a thickness of 0.5 mm. and weighing about 22 g. per square m. 10 such webs are laid on top of one another with the adjacent webs being arranged at angles to each other, and the laminated structure is passed between heated rollers to form a fleece weighing about 200 g. per square m.

One surface of this fleece is treated with a foam comprising 10 volume parts of air per volume part of -a liquid dispersion containing about 10% by weight of solid binder The pre-treated fleece is dried to cause deposition of about 6 parts by weight of solid rubber on the surface of the fleece per parts by weight of fibers (12 g. per square m.).

Then, a foam containing 5 volume parts of air per volume part of liquid material is pressed into the untreated surface of the fleece. The liquid dispersion us d r the formation; of 'this foam' has the same .composition as that used :for' .the'pre treatment except that it contains; instead of 826.5 parts by weight of softened water, only 226.5 parts by weight of softened water. Thus, this dispersion contains 25 by weight of binder solids, and 4% by weight of wetting agents.

The penetrating foam serves to incorporate into the fleece about 94 parts by weight of binder solids per 100 parts by weight of fibers. Simultaneously, the fleece is compressed and stretched lengthwise. The impregnated sheet is stabilized by drying and vulcanization without pressure, then washed and dried again.

The length of the finished sheet exceeds that of the original fleece by about 25 while its fiber weight per square mgis about 20% less than that of the starting fleece. The final,- porous sheet material has a thickness of about 0.3 mm, weighs 320 g. per square and contains.aboutz50% by weightof solid rubber andabou-t 50% by weight of fiber material.

Exemplar; A-fi-ber mixture is prepared of fine cardable .fibers as follows: I

Per cent by weight Cotton 30 Ramie 30 Rayon 40 The mixture is formed into webs consisting of inter mingled and polyposed fibers, each web having a thickness of about 0.15 and weighing about 1 5 g. per square 111. Three webs are placed on top of one-another. After pressing of the multi-layer structure between heated rollers with slight longitudinal stretching, a fleece is obtained having a thickness of about 0.5 mm. and weighing about 40 grams per square meter.

A foam comprising about 9 volume parts of air for each volume part of liquid is formed from a dispersion containing about 8% by weight of binder solids and ha ing the followingcomposition:

.Liquid- I send Weight, Content, 1 parts parts Polyvinyl chloride emulsion (40%). 250. 100 softened water 982 Wetting agent 18 18 Liquid Solid Weight, Content,

parts :parts Polyvinyl chloride emulsion (40%). 100 40 Polymethylmethacrylate emulsion (40%) 200 80 Wetting agent 10 10 Soitened water V V V 170 Through selection of the spacing betweenrollers .26, 27 about 35 parts by weight of binder material .are incorporated into the fleece per 1.00 parts by weight of fiber. The material is then dried without pressure by passing it through a dryingchamber, washed in cold water and .dried again.

. 'Ilhe-resulting-sheet material has a thic'knesslofi about 0.14- mm. and a'weight of about 48 g. per .mi Its Ieiigth exceeds that of the original fleece by about 3'3 /s-%-.of the starting length, while its fiber content per m. is about 25 less than that of :the starting fleece. The material contains about 33 /3% by weight of solid thermoplastic binder material. .It is shrink-proof, air and waterpermeable and can be adhered to fabrics by hot ironing on the fabrics. In' constitutes a suitable stiffening material for shirt collars and cuffs and other washable garments, such as blouses, as described specifically in .my U. patent application Serial No. 262,945, filed December 22, 1951, which is a continuation-in-part application of my copending United States patent application Serial No.-.l02,423,, filed on June 30, 1949.

Example 7 A fiber mixture consisting of 50 parts by weightof cotton and 50 parts by weight of ramie is formed into webs having each a .thickness of 1.2 mm. and a weight of .35 g. per square meter. 30 such webs are combined into a fleece having a thickness of 40 mm. and a weight of 1000 g. per s'quare' m. p

This fleece is treated on one surface with a foam containing about 10 volume parts of air per volume part of a liquid dispersion containing 5% by weight of a' filmforming :binder :material having the following composition:

iquid Solid Parts Parts- B. W. B. W.

natural rubber latex (70%) 70 .50 softened water 899. 6 wetting agent 25 25 zinc oxide 3 3 colloidal sulphu 2 2 ultravulcanlzation-accelerat 0.5 0:5

"surface thereof by means of a pair of pressure rollers.

The liquid binder contains about 40% I of binder solids, about 10% of wetting agent and about 2% of foam stabilizer. It has the following composition:

Liquid Solid Parts Parts 3. W. B. W.

butadtenczstyrenepolyimerilatex (60%)--.." 335 i .200 softened wliter 86.5 sodtmn-isdbutylene-naphthalene sulionate (web ting agent).- 50 50 c oxide, .h- 10 10 colloidal-sewn 6 6 raytilcanimtian acoelera 2.5 2..5 methylcellulose 10 10 During its passage between .the pressure rollers, the fleece is compressed and stretched lengthwise while about 1.12 ,parts by weightof binder solids .are incorporated into .the fleece per ,1.0.0 .parts by weight of fibers. The impregnated sheet is stabilized without pressure by drying with heat-"and vulcanization :bystorage for 12 .hours'in a room Heated.to about..C. Thereafter the sheet is washed and dried again. I k I .Theiinishedasheet is about ..25% longer and-contains about 20% by weightless fibers .thanthe starting fleece. The final product has a thickness of about 3.5 mm. and

11 weighs about 1700 g. per square m. It contains about 53% by Weight of solid binder material and 47% by weight of fibers. The material may be used as a scrubbing cloth.

Example 8 Liquid Solid Parts Parts B. W. B. W.

polyvinylidene chloride emulsion (50%) 240 120 softened water 720 wetting agent 40 40 Upon drying, about 13 parts by weight of solid polyvinylidene chloride are deposited on the treated surface of the fleece per 100 parts by weight of fibers (13 g. per square m.).

Thereafter, a creamy, flowable foam containing about 6 volume parts of air per volume part of liquid binder is pressed into the untreated surface of the fleece. The liquid binder contains about 40% by weight of binder solids, about 7% by weight of wetting agent and about 3% by weight of foam stabilizing agent and has the fol- As the foam is pressed into the fleece to effect uniform and complete penetration thereof, the fleece is reduced in thickness and stretched lengthwise while about 287 parts by weight of binder solids are incorporated into the fleece per 100 parts by weight of fibers.

The impregnated sheet is stabilized without pressure by heating and drying, then carefully washed in cold water, dried again, and finally lightly calendered.

The finished sheet is about 22% longer and contains about 18% by weight less fibers than the starting fleece. The sheet material has a thickness of 1.0 mm. and a weight of 320 g. per square m. It contains about 75% by weight of solid binder material.

Example 9 taining about 13 volume parts of air per volume part of a v liquid, film-forming binder containing about 10% of binder solids and having the following composition:

Liquid Solid Parts Parts 13. W. B. W.

chloropreue latex (50%) 100 50 softened water 350 wetting agent. 30 30 zinc oxide 15 15 colloidal sulphur 1 1 ultravuleanization ace erato 2 2 antioxidant 2 2 Upon drying, a surface impregnation is obtained which contains about 8 parts by weight of binder solids per 100 parts by weight of fibers (4 g. per square m.).

Thereafter, a thick, flowable foam containing about 7 volumes of air per volume part of liquid binder is pressed into the untreated surface of the fleece. The foam is prepared from a binder liquid which contains about 25% of binder solids and about 6.3% of wetting agents and which has the following composition:

The foam is rolled into the fleece with light pressure to cause incorporation into the fleece of about 52 parts by weight of solid binder material per 100 parts by weight of fibers.

After drying without pressure, washing with cold water and drying again, the final sheet material, the length of which exceeds that of the starting fleece by about 33 /3 has a thickness of about 0.2 mm. and a weight of about 60 g. per square meter. It contains about 38% by weight of solid binder material and about 62% by weight of fibers.

Example 10 A fiber mixture consisting of 100% by weight of Egyptian cotton is formed into a single layer fleece having a thickness of about 1.0 mm. and weighing about 35 g. per square meter.

This fleece is treated on one surface with a foam containing about 12 volume parts of air per volume part of a binder liquid containing about 9% by weight of binder solids and about 4% by weight of wetting agent and having the following composition:

Liquid Solid Parts Parts B W. B. W

copolymer of vinyl chloride and vinyl acetate dispersion (60 u) 45 softened waten 405 wetting agent 20 20 500 On drying, a slight surface cohesion is obtained and about 30 parts by weight of binder solids are deposited on the treated surface of the fleece per parts by weight of fibers in the fleece (10.5 g. per square m.).

Thereafter, a foam containing about 12 volume parts of air per volume part of liquid binder is introduced into the untreated surface of the fleece. The liquid binder 13 contains about 18% by weight of solid binder material and about 6% by weight of wetting agent and has the Forty-five parts by weight of binder solids are incorpo- The ressure Withwhich the foamzis (pressed. inte the fleece is so adjusted that about 70 partsioyi' weight of solid binder are incorporated into the fleece per 100 parts by weight of fibers'.

After drying and vulcanization, both without pressure, followed by washingand drying, the resulting final-sheet material has a- .thicknessof 1.2 mm. and. .a weightf 420 g. per square m. Its length; exceedsthat of the-starting fleece .by about 2:5 %1,-its :fiber weight per square, m. is about 20% less-than thatof the starting-fleecealt-contains about 43% by weight of solid binden-particles and by weight of fiber material,

about 57% Example" 12 -.A fiber mixture, consisting tof ,50 parts by weighttof rated into the fleece per 100 parts by weight of fibers .15 a p g from the smnd foam impregnation The sheet isdried asoestosfibers and 50 .parts by we ght of-glassfibers s without pressure, then washed with cold water and finally formed into webs having each a thickness of about 0.2 dfledUagaJ-n at modemteheah mm. and a weight of 25 g. per square m.

During the variousstages-of the process the material is Y F F combmed by piessure f heat longitudinally stretched to about 143% of the original 20 i Stretchmg mm a fleece havmg welght of length of the fleece while the fiber weight .per squarem. 280 5' Per Equine meten t t is reduced by about 30%. The finished product has a Thls F treated "F 9 i 9 .F ,-W thickness of 0.1 mm. and a weight of 43 g. per square foam Containing? elachivolunie partof hq d b f m. It contains about 43% by weight of solid binder ma- "9 parts. i t l i ls ifPi lfifi f terial and about 57% by weight of fibers. The sheet mahquld comammg 8% by Y g f teria'l may be used as a lining-or iriterlining, where a very a d, 4% W P ma is agf such bmder thin'and light material is required, or as a substitute 'for hquld having the followmg composltlon:

cheesecloth.-

Example 11 ggg l gg lg.

Intermingled polyvinyl chloride fibers are formed into H 4 jw' thin webs having each a thickness of 0.2 mm. and a I 0 p weight of 18 g. per square in i8 such webs are com- 331353 32235]?ffffffi 23 Q2 l bmed by pressure and heat with, slight stretching into a wetting again..- "20 go fleecehaving a weight of about 300 g. per square m. fi aggfggjgggg f 5 This fleece is treated on one of its surfaces with a foam ul a l n a accelerator Q9 containing about 10 volumes of air for each volume of 500 a liquid, film forming binder material having the followt t 3 mg composmon' Upon drying, the foam is caus'edto collapse and to 140 deposit on the treated surface about 6 parts by weight ggg of binder solids per 100 parts by weight of fibers (17 g. .B. W. 1 .w. per square 111.), thus eifccting a light surface cohesion of the fleece. polybutadienestyrenelatex (40% 25o 10o Thereafter, a creamy, flowable foam containing about g gffg ggg f- 25 2-volume parts of air per volume part of liquid binder'is zinc pxide- 5 5 cautiously introduced into the fleece through the untreated ffi ggfig gggz accimorflh 3' i surface thereof bymeans of rollers adjusted tie-minimum pressure. The liquid binder used for the preparation of I 19000 this foam containsabout 22% by weight of binder solids andabout 3% by weight of 'a wetting agent and has the The mixture contains about 10 parts by weight of the following composition: binder solids in 100 parts by weight of liquid.

Upon drying, about 5 parts by weight of binder solids Li um Solid are deposited on the treated surface of the fleece per 100 P rts Parts parts by weight of fibers (15 g. per square m.), 5 p

Thereafter, a flowable foam containing about 3 volume v parts of air per volume -part of liquid binder is pressed g f g f gzgg late $22 5 into the untreated surface of the fleece. The liquid binder wetting again?" I 15' i" used for the preparation of the foam contains about, gg fggiiga m f f 28% by weight of binder solids, about 6.5% by weight 60 anti-oxi t 1 :1 of wetting agent and about 2% by weight of foam ultravulcamzamn accelerator m 1 stabilizing agent and has the following composition: 500

Liquid Solid the" .foamis vpassed into the fleece, the latter is gag? gag? stretched lengthwisewhileabout 100 parts of solid rubber are incorporated into the fleece per 100 parts by ohloroprene latex '100 70 weight softened water un -c- 116 The resulting porous sheet material is then carefully g gg g gyfi ff it 16 V16 dried without pressure, vulcanized without pressure, gu t: agingll l 70 washedand dn'ed again. f g g f The overall stretch throughout the process amounts to anti-0X p 1 1 about 17.5% of the original length of the fleece corremethylceuulose (foam stabmzmg'agent) 5 5 sponding' to a reduction of fiber weight per square m. of about 15%. The final sheet has a thickness of 3 mrri. and a weight of 490 g. per square m. It contains about 1 51.5%. by weight of binder solids and 48.5% by weight of fiber material.

Example 13 A fiber mixture is prepared consisting of 80 parts by weight of cotton and 20 parts by weight of wool. This mixture is formed into webs having each a thickness of 0.4 mm. and a weight of 19 g. per square in.

Six such webs are combined with pressure and slight stretching into a fleece having a weight of about 105 g. per square m.

This fleece is treated on one of its surfaces with a foam containing for each volume part of liquid about volume parts of air. The foam is prepared from a binder 16 Example 14 i A fiber mixture containing 50% by weight of cotton and 50% by weight of rayon was formed into loose,

light webs having each a thickness of about 0.5 mm. and

a weight of about 26 g. per square n1. Twelve such webs are'cornbiued with pressure and heat and slight longitudinal stretching into a fleece weighing about 300 g. per square m. p 7

This fleece is first treated by spreading on one surface thereof a flowable foam containing about 10 volume parts of air per volume part of a 14% synthetic rubber dispersion of the following composition:

liquid containing about 8% by weight of binder solids id 8 m and having the following composition: 35 Parts B. W. B. W.

Liquid Solid butadiene acrylonitrile polymer dispersion (37%).- 270 100 Parts Parts wetting agent solution (53%) 120 60 B. W. B. W. vulcanizing agents and other ingredients (dispersions) 20 10 softened water 290 butadiene acrylonitrile dispersion (37%) 270 100 wetting agent solution (50%) 54 27 700 dispersion 33%%:

- z coxide 7.5 2.5

colloidal sulphur 7.5 2.5 ultravulcamzation 081m 3 1 About 3.5 parts by weight of vulcaulzable binder sohds antioxidant 3 1 softe ed water w 905 are deposited on the treated surface per 100 parts by 1 250 weight of fibers (10.5 g. per square n1.) when the fleece is dried.

Upon drying of the foam, about 4.5 parts by weight of binder solids are deposited on the treated surface per 100 parts of fibers in the fleece (5 g. per square m.). This deposition effects a light surface cohesion of the fleece.

Thereafter, a heavier foam containing about 5 volume parts of air per volume part of a 14% aqueous binder dispersion is pressed by means of pressure rollers into the untreated surface of the sheet. The binder dispersion had the following composition:

-The foam is dried without pressure and about 21.5 parts by weight of vulcanizable binder solids are deposited throughout the fleece per 100 parts by weight of fibers.

The fleece is stretched lengthwise during the prestabilizing stages of the process to about 125% of its original length with reduction of its fiber weightby about 20%.

The resulting sheet material is carefully dried without pressure and Without complete vulcanization. When washed with cold water, it has a thickness of about 1.5 mm, weighs about 106 g. per square m. and contains about 21% by Weight of binder solids and about 79% by weight of fiber material.

This sheet material has high Water absorbent properties but relatively low tensile strength and abrasion resistance. It is particularly suitable as an intermediate in the preparation of porous, water absorbent sheet materials in ac oordance with the invention described in my United States application Serial No. 262,943, filed December 22, 1951, which is a continuation-in-part of my United States application No. 102,424, filed on June 30, 1949.

scribed stages of the process, the fleece,

Next a heavy, creamy foam containing about 3 volume parts of air per volume part of liquid is pressed into the untreated surface of the fleece by means of pressure rollers. The binder liquid used for the preparation of the foam contains 25% by weight of binder solids and has the following composition:

Liquid Solid Parts Parts B. W. B. W.

butadiene aerylonitrile polymer dispersion (37%) 270 100 wetting agent solution (66.6%) 90 60 vuleanizing agents and other ingredients (dispersions) 20 10 softened water 20 Example 15 A fiber mixture is prepared from by weight of synthetic protein fibers and 20% by weight of cotton fibers.

The mixture is formed into loose webs having a thickness of 0.25 mm. and a weight of 22 g. per square m.

Twenty such webs are placed at an angle on top of one another and the resulting multilayer structure is condensed with heat and pressure and slight longitudinal stretching to produce a fleece weighing about 400 g. per square m. This fleece is passed in a continuous system .at a comparatively high speed through the following impregnating stages. I

In the first stage, a foam comprising about 10 parts of air for each part of liquid and formed from a dispersion containing about 10% by weight of binder solids is spread .17 i uniformly on one surfaceof :thefleece. .Thebinder. .persion has the following composition:

l Liquid Parts ."B. -W.

Solid line oxidedispersion (50%) butadiene acrylonitrile polymendisper'sion (40%) sodium) 'lauryl suh'onate :solution I (wetting agent); a

ultra-vulcanization acceleratorjdispersion (25% 6 sulphur dispersion 50% "II antioxidant dispersion (50% softened water On *drying, about '3 parts by weight of solid'binder 'material' are deposited per 100 parts' by'weight of fibers (about-9.5 g. per'sguare'm.),thus producing'a light sur- 'facecohesion.

In the second impregnating stage, afoam comprising about '3 volumeiparts of air per volumejpart of liquid is pressed into the opposite untreatedsurface of "the fleece. Thisfoam is.prepared'from-,a dispersion containing about 30% by weight of bindersolidsand .havingthe 'following composition:

v.Liquid IRarts .EBEW.

. sodium isobutylene naphthalene'solution (wetting zinc oxide dispersion (50%) softened water butadiene acrylonitrile pOl mer 'dispersiOn '(50%) 5.150

.a ent (60 7) ult a viilcani ation accelerator dispersion (25%) 8 sulphur dispersion {50%) "II 1'6 antioxidant dispersion (-50%) IOWKDNO About 72parts by' weight'of 'solid'binder material are incorporated into the fleece per 100 parts by weight of fibers. The material is then dried and vulcanizcd'without pressure by passing it through a heated chamber, then washedtand dried again. During the various impregnating and drying stages prior .to. the vulcanization: of the last introduced hinders, the material undergoes .a. longitudinal stretching to about twice the. length of the original .fleece and correspondingly the fiber content 10f the material per square to. is reduced-about 50% by weight.

Theresulting sheet material has a thickness of about l.2 .mm. and aweight'of about 350 g. per square m. It contains about 43% 'by weight of vulcanized ;binder solids. It is shrink-proof, air permeable and elastic. It has a fabric-like soft hand and is suitable as a heavy duty, warm 'inte'rlining, affording excellentwind protection.

Example 16 1 A'fiber mixture is prepared from 60% by weight of spun rayon, 20% by weight of ramie and 20% by weight of polyacryl fibers.

The mixture is'formed into loose webs having a thickness of 0.3mm. and a weight of 25g. per squarem.

Twelve such Webs are placed at an oblique angle on top of one another and the resulting multi-layer structure is condensed with 'heat and pressure and slight longitudinal'stretching to produce 'a 'fieece weighing about 280 g;per'square m.

Thisfleece is treated by spreading on one surface thereof a foam comprising aboutl0parts of airfor each part of"li quid,"s aid foam being formed from'a dispersion rsodfiibim lauryl sult'onate solution (wetting agent) '.materialare deposited points between containing about "8% 'by weight ofYbinderssolids and having .the followingcomposition:

-' 1 Liquid Y Parts B.=W.

Solid iParts BEW.

polyacrylonltrile dispersion 40%) 200 sonata-aria;

) On drying, :aboutl3 'parts 'by weightof'isoliddbinder per parts .by weightzofzfibers (about 8.4 g. per square 111.), .thusxproducing a, light'surface cohesion. 1

In the through-impregnating-stage, a. foam comprising about 2 volume. parts of. airv per volume .part of,:liq.uid,-1is pressed-intothe opposite untreated surface of. the :fleece. This foam .is preparedxfrom a dispersion containingiabout 25% .by weight of binder solids andhavingtheifollowing composition -About-'40-parts by weight 'of solid-binder material are incorporated 'intothe eece per "l00'-parts"by weight of The -mate'rial"is then' dried Without pressure by passing' it through a chamber heated 'to' -"C.for 50 :minutes, and thereafter*lightly'calentlered, washed arid dried again. Duringthelvarious impregnating stages "the material "undergoes taslongitu'dinal stret'c'liing by"about "82% of the original length-of'the fleece and the fiber content per' square m. is reduced about 4 5% by dl The resulting sheet niater'ial has -"a thiknessdf 0281mm. and a weight of about 224%: per square-m. It cont-ains about 30% i by weight of= thennoplast'ic binder solidsf'it 1 is shrink-proof, airand Water-permeable, and fond-holding. It is suit able as a'strong interlining for sport'shirts, '-work blouses'and the like.

It should be understood that the foregoing' examples are not intended to limit the scope of my invention, and

that variousmo'difi'eationsand changesare-posSiblewithin this scope.

What I claim is: l. -A process imthe manufacture "of porous, eair- -zperrneable fiexible sheet material, --said process compi'ising the steps of 'preparing a loose fleece of intermingled, pol-yposed, fine,cardable fibers, saidlleeceweighing' about 35 g. to about IOOO-g. per square m pro-treating one surface 'of said fleece toproduce a light-surface cohesion without any appreciable loss of the porosity ofLthefleece, then introducing an aqueous film-formingbinder "matcrial-containing about 14% to about 40% by' wei'ght of binder solids and being in the form of a stable' flow'able .foam into the Efieece through the untreated surfacethereof under 'a pressure. to effect aysubstantially zcomplete'zand uniform penetration of the Ifleece with simultaneous :de-

.struction ofpart of the foam cellsand .preservation'of numerous :relatively large interstices :b'etween theofibers,

.and drying without pressure to effectcomplete collapse .of the remaining foam cells and .precipitation..of;the

binder material on the fibersparticularlyiatthe;c1ossing adjacent fibers, uniformly throughout. the fleece in the form. of small, filmy particles of binder solids adhering to the fibers and cementing them together at their crossing points without completely encasing the fibers or filling the interstices therebetween to any substantial extent so as to stabilize the fibers in the form of an open skeleton.

2. A process as claimed in claim 1, in which the aqueous film-forming binder material is a vulcanizable latex of the group consisting of the natural and synthetic rubber latices, and the fleece is dried and vulcanized without pressure after the latex foam has been pressed into its untreated surface. 7 I

3. A process for the manufacture of porous, airpermeable, flexible sheet material, said process comprising the steps of preparing a loose fleece of intermingled, polyposed, fine, cardable fibers, said fleece weighing about 35 g. to about 1000 g. per square m., pre-treating one surface of said fleece to produce a light surface cohesion without any appreciable loss of the porosity of the fleece, then introducing an aqueous, film-forming binder material containing about 14% to about 40% by weight of binder solids and up to about 60 parts by weight of a wetting agent per 100 parts by weight of binder solids in the form of a stable flowable foam into the fleece through the untreated surface thereof under a pressure to effect a substantially complete and uniform penetration of the fleece with simultaneous destruction of part of the foam cells and preservation of numerous relatively large interstices between the fibers, and drying without pressure to effect complete collapse of the remaining foam cells and precipitation of the binder material on the fibers particularly at the crossing points between adjacent fibers, uniformly throughout the fieece in the form of small, filmy particles of binder solids adhering to the fibers and cementing them together at their crossing points without completely encasing the fibers or filling the interstices therebetween to any substantial extent so as to stabilize the fibers in the form of an open skeleton.

4. A process for the manufacture of porous, airpermeable, flexible sheet material, said process comprising the steps of preparing a loose fleece of intermingled,

polyposed, fine, cardable fibers, said fleece weighting about 35 g. to about 1000 g. per square m., pre-treating one surface of said fleece by applying to said surface a quantity of a first binding agent in a carrier liquid in the form of a stable, relatively stiff foam to produce a light surface cohesion without any appreciable loss of the porosity of the fleece, drying the fleece to effect stabilization of the binder by removal of the carrier liquid, then introducing an aqueous, film-forming binder material containing about 14% to about 40% by weight of binder solids and being in the form of a stable flowable foam into the fleece through the untreated surface thereof under a pressure to eifect a substantially complete and uniform penetration of the fleece with simultaneous destruction of part of the foam cells and preservation of numerous relatively large interstices between the fibers, and drying without pressure to effect complete collapse of the remaining foam cells and precipitation of the binder material on the fibers particularly at the crossing points between adjacent fibers, uniformly throughout the fleece in the form of small, filmy particles of binder solids adhering to the fibers and cementing them together at their crossing points without completely encasing the fibers or .filling the interstices therebetween to any substantial extent so as to stabilize the fibers in the form of an open skeleton.

5. A. process for the manufacture of a fabric-like,

porous, shrink-proof, air-permeable sheet material resistant to creasing, which comprises the steps of preparing a loose fleece consisting of a plurality of superposed webs of fine, cardable fibers arranged in a plurality of intersecting directions, each web having a thickness of about 0.1 mm. to 1.2 mm. and weighing from about to 35 g. per m? and the fleece weighing from about 40 to 400 g. per m5, treating at least one surface of said fleece with a liquidto eflect a light surface cohesion without appreciable reduction of the porosity of the fleece, drying the fleece to remove-the liquid, pressing into the pretreated fleece, through at least one surface thereof, an aqueous film-forming binder material containing about 14% to about 40% by weight of binder solids and being in the form of a stable, flowable foam under a pressure to cause a substantially complete and uniform penetration of the fleece with simultaneous destruction of part of the foam cells and preservation of a substantial porosity in the impregnated sheet formed, and drying the impregnated sheet without pressure, thus destroying the remaining foam cells and precipitating solid, filmy binder particles on the fibers uniformly throughout the fleece to cement the fibers together at their crossing points.

6. A process for the manufacture of a fabric-like, porous, air-permeable, shrink-proof, isoelastic sheet material, which comprises the steps of preparing a loose fleece consisting of a plurality of superposed webs of fine, cardable fibers arranged in a plurality of intersectingdirections, each web having a thickness of about 0.1 to about 1.2 mm. and weighing from about 5 to about 35 g. per m. the fleece weighing from about 40 g. to about 400 g. per m? and containing at least 15% b. w. of fibers of high elasticity, applying to at least one surface of said fleece a quantity of a first binder material in a liquid carrier to cause a light surface cohesion without appreciable reduction of the porosity of the fleece, drying to stabilize said first binder by removal of the carrier liquid, pressing into the pretreated fleece through at least one surface thereof a quantity of a vulcanizable, elastic, fihnforming binder material containing about 14% to about 40% by weight of binder solids and being in the form of an aqueous foam under a pressure to cause a substantially complete and uniform penetration of the fleece with partial destruction of the foam cells and incorporation into the fleece of about 20' parts to about parts (solid weight) of binder material'per 100 parts, by weight, of fibers while maintaining a substantial porosity in the impregnated sheet formed, and stabilizing the impregnated sheet by drying and vulcanization of the vulcanizable binder material without pressure, thus causing complete destruction of the remaining foam cells and precipitation of solid, filmy binder particles on the fibers uniformly throughout the fleece to cement the fibers together at their crossing points. i v

7. A process as claimed in claim 6, in which the elastic, film forming binder material is a latex selected from the natural and synthetic rubber latex dispersions of vulcanizable solids containing further a wetting agent, a foam stabilizing agent, a vulcanizing agent, a vulcanization ac celerator and an antioxidant.

8. A process for the manufacture of a fabric-like porous, air permeable, isoelastic sheet material which comprises the steps of preparing a loose fleece consisting of fine cardable fibers arranged in random positions, said fleece containing at least a major proportion of fibers of high elasticity and weighing about g. per m. applying to at least one surface of said fleece a small quantity of a flowable binder, causing said binder to solidify to impart to the fleece an initial surface cohesion without appreciable reduction of its porosity, pressing into the pretreated fleece through at least one surface thereof an aqueous dispersion of vulcanizable elastic binder containing about 14% to about 40% by weight of binder solids and being in the form of an aqueous foam so as to cause a substantially uniform pentration of the fleece with incorporation therein of about 33 /3 parts to 100 parts (solid weight) of binder material per 100 parts by weight of fibers under a pressure to reduce the thickness of the fleece to 0.2 to about 0.5 mm. with preservation ofya substantial porosity in the impregnated sheet formed, and stabilizing the impregnated sheet by vulcanization.

9. A process for the manufacture of air-permeable, flexible, fibrous sheet material, said process comprising the steps of forming a loose fleece of intermingled, polyposed, fine, cardable fibers weighing about 35 to about 1000 grams per square meter, pre-treating at least one surface of said fleece to produce a light surface cohesion without any appreciable diminution of the porosity of the fleece, introducing into said pre-treated fleece an aqueous emulsion of a film-forming binder material containing about 14% to about 40% by weight of binder solids and being in the form of a stable, flowable foam under a pressure suflicient to effect a substantially complete and uniform penetration of the fleece with simultaneous destruction of part of the foam cells and compaction of the fleece to a sheet without substantial reduction of the interstices between adjacent fibers in the plane of the sheet, and drying without pressure to eflect complete collapse of any remaining foam cells and setting of the binder solids precipitated primarily at the crossing points between adjacent fibers uniformly throughout the sheet in the form of small, filmy particles adhering to the fibers and cementing them together at their crossing points without filling the interstices between the fibers to any substantial extent whereby the sheet is stabilized in the form of an open skeleton.

10. A process for the preparation of unwoven thin porous sheet material having a thickness ranging from about 0.1 to about 3.5 millimeters and a weight of about 40 to about 1700 grams per square meter, the sheet material having a textile character, softness, good hand, flexibility, isoelasticity, good resiliency, crease and crumple resistance, and permeability to air, water and perspiration, said process comprising the steps of forming a thin fleece of cardable fibers arranged in a plurality of intersection directions and weighing about 35 to about 1000 grams per square meter, applying to one surface of said fleece a thin layer of adhesive so that the fibers are held fleece in the form of a stable flowable foam, whereby said fleece is reduced in thickness to a thin sheet and said foam is uniformly distributed throughout said sheet, a portion of the foam cells being collapsed during introduction into said fleece, drying the impregnated sheet without pressure to thereby complete destruction of the foam cells and convert the binder to thin filmy webs which cement the fibers together at their crossing points to retain the structural character of said sheet without afiecting the porosity thereof, thereafter washing said sheet in Water to remove water-solubles together with said wetting agent, and drying said sheet.

References Cited in the file of this patent UNITED STATES PATENTS 1,899,535 Teague Feb. 28, 1933 2,003,935 Howard June 4, 1935 2,055,410 Hurst et al. Sept. 22, 1936 2,140,026 Murphy et al. Dec. 13, 1938 2,140,063 Talalay Dec. 13, 1938 2,256,034 Nottebohm Sept. 16, 1941 2,298,986 Taylor et al. Oct. 13, 1942 2,341,130 Unsworth Feb. 8, 1944 2,533,167 Kilhom Dec. 5, 1950 2,571,334 Browne Oct. 16, 1951 2,580,202 Talalay Dec. 25, 1951 FOREIGN PATENTS 468,861 Great Britain July 14, 1937 

1. A PROCESS FOR THE MANUFACTURE OF POROUS, AIRPERMEABLE, FLEXIBLE SHEET MATERIAL, SAID PROCESS COMPRISING THE STEPS OF PREPARING A LOOSE FLEECE OF INTERMINGLE POLYPOSED, FINE, CARDABLE FIBERS, SAID FLEECE WEIGHING ABOUT 35 G. TO ABOUT 1000 G. PER SQUARE M., PRE-TREATING ONE SURFACE OF SAID FLEECE TO PRODUCE A LIGHT SURFACE COHESION WITHOUT ANY APPRECIABLE LOSS OF THE POROSITY OF THE FLEECE, THEN INTRODUCING AN AQUEOUS, FILM-FORMING BINDER MATERIAL CONTAINING ABOUT 14% TO ABOUT 40% BY WEIGHT OF BINDER SOLIDS AND BEING IN THE FORM OF A STABLE FLOWABLE FOAM INTO THE FLEECE THROUGH THE UNTREATED SURFACE THEREON UNDER A PRESSURE TO EFFECT A SUBSTANTIALLY COMPLETE AND UNIFORM PENETRATION OF THE FLEECE WITH SIMULTANEOUS DESTRUCTION OF PART OF THE FOAM CELLS AND PRESERVATION OF NUMEROUS RELATIVELY LARGE INTERSTICES BETWEEN THE FIBERS AND DRYING WITHOUT PRESSURE TO EFFECT COMPLETE COLLAPSE OF THE REMAINING FOAM CELLS AND PRECIPITATION OF THE BINDER MATERIAL ON THE FIBERS PARTICULARLY AT THE CROSSING POINTS BETWEEN ADJACENT FIBERS, UNIFORMLY THROUGHOUT THE FLEECE IN THE FORM OF SMALL, FILMY PARTICLES OF BINDER SOLIDS ADHERING TO THE FIBERS AND CEMENTING THEM TOGETHER AT THEIR CROSSING POINTS WITHOUT COMPLETELY ENCASING THE FIBERS OR FILLING THE INTERSTICES THEREBETWEEN TO ANY SUBSTANTIAL EXTEND SO AS TO STABILIZE THE FIBERS IN THE FORM OF AN OPEN SKELETON. 